1. Field of the Invention
The present invention relates to a bandsaw machine provided with an endless bandsaw blade, and, in particular, to a method and device for measuring the cross sectional external form and dimensions of a workpiece being cut in the bandsaw machine and a device for automatically adjusting the position of a blade guide to conform to the external form of the workpiece.
2. Description of the Prior Art
When a workpiece is cut by a bandsaw blade, it is advantageous to know in advance the cross sectional external form and dimensions of the workpiece in order to avoid an erroneous cutting due to misjudgment in the workpiece supply and also in order to adjust the position of a saw blade guide to conform the external form of the workpiece.
Conventionally, the operator generally uses a scale to measure the shape and dimensions of the workpiece. Devices have been proposed to make such measurements automatically, such as the device with the configuration outlined in U.S. Pat. No. 4,432,260. In the above-mentioned prior art, when the workpiece is measured using a scale means connected to the vise device, and the height of the workpieces is measured using a scale means in the vertical direction. Accordingly, it is possible to measure the width and the height of the workpiece automatically. However, there is no facility for judging if the shape is square or circular, and therefore the judgment of the shape of the workpiece is dependent on the observations of the operator.
In recent years, the need has arisen for a device to automatically convey a workpiece into the sawing machine to allow the cutting of many different types of workpieces automatically. This requires automatic measurement of the shape and dimensions of the workpiece in the sawing machine.
In addition, it is desirable to be able to reduce the distortion and the vibration of the bandsaw blade of a bandsaw machine when cutting into the workpiece.
Regardless of the type--horizontal or vertical--for a bandsaw machine it is normal to provide a saw blade guide for guiding the saw blade on each side of the workpiece. Conventionally, one of these saw blade guides is set in a fixed position while the other is usually adjusted beforehand to a position conforming to the maximum width of cut in the workpiece. Accordingly, when, for example, the workpiece is a round rod, the spacing of the saw blade guide is set large enough to conform to the diameter of the round rod. For this reason, when the saw blade first contacts and begins to cut into the round with respect to the dimensions of the spacing of the blade can be produced.
Specifically, in a conventional bandsaw machine the adjustment of the position of the saw blade guides must be performed manually. The problem therefore arises that, not only the adjustment of the blade guide position requires a great deal of trouble, but also bending of the saw blade readily occurs at the first cut.
In consideration of the problems associated with such conventional devices, technology has been developed to automatically adjust the spacing of the saw blade guides to conform to changes in the length of the cut in the workpiece. Specifically, such technology is disclosed, for example, in U.S. Pat. No. 4,363,254. This prior art incorporates a configuration in which one of the saw blade guides is moved by means of a hydraulic cylinder which is controlled by a changeover valve, and the changeover valve is controlled by means of a profiling contact member which is moved by the workpiece. Accordingly, in this prior art, as the saw blade advances to cut into the workpiece, the configuration limits the form of the workpiece. Specifically, when cutting a workpiece with a complicated form, for example, joist or I beam, the contact member may lose the shape of the workpiece to trace or cause a defective conflict between the blade guide and the workpiece.